ese206 SP 2019 lecture 1 intro · Develop an understanding of the Bipolar Junction Transistor (BJT) and its operation. Identify and describe the different BJT configurations, DC biasing,

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Lecture 0

Course Overview

EE206 Electronics I

• Course description: Theory, characteristics and operation of diodes, bipolar junction transistors and MOSFET transistors.

• When: Tue Thu 10:30-12:20 (Lectures)

• Textbook: Fundamentals of Microelectronics; 2nd ed. Razavi•Recommended references supporting the course

B. Streetman, S. Banerjee (1999).Solid State Electronic Devices, PrenticeHall, ISBN 0130255386.Robert L. Boylestad, Louis Nashelsky, (2013) Electronic devices and circuittheory, 11th edition, Pearson EducationNeamen D.A., (2007), Microelectronics Circuit Analysis and Design,McGraw Hill.

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Course Assessment

Lecture 01 3

Assessment Type Percentage Time

Midterm 20% Week 8

Lab 20%Every 2 Weeks

Assignment/Quiz 20% Every Week

Final Exam 20% Week 16

Project 20% Week 17

Total mark 100%

Weeks Topics

1 Introduction, Basics of semiconductor physics

2 Intrinsic & Extrinsic semiconductors

3 PN-junction4 PN-diodes and their applications5 Bipolar junction transistor (BJT) I6 Bipolar junction transistor (BJT) II7 Bipolar junction transistor (BJT) III8 Midterm9 FET transistor I

10 FET transistor II11 FET transistor III12 CMOS Technology13 CMOS Amplifiers14 OPAMP as a black box

Syllabus

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Prerequisite: Circuit Theory– Ohm’s law– Series/parallel circuit– Voltage/current divider– Nodal analysis– Mesh analysis– Dependent sources– Thevenin and Norton Equivalent Circuit– AC analysis

Course Objectives

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Identify and describe operation of semiconductor devices throughunderstanding of the semiconductor physics.

Develop an understanding of the PN junction diode and its behavior. Develop an ability to analyze diode circuits and examine additional

applications of the diode. Develop an understanding of the Bipolar Junction Transistor (BJT) and

its operation. Identify and describe the different BJT configurations, DC biasing, and

AC analysis. Develop an understanding of the Field Effect Transistor (FET) and its

operation. Identify and describe the different FET configurations, DC biasing, and

AC analysis. Develop an understanding of the CMOS circuit and its operation. Develop an understanding of the OPAMP circuits.

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EXPECTED OUTCOMEUpon successful completion of the course, students will be ableto: Acquire some understanding in the fundamental electric and

electronics principles. Describe the operation and i-v characteristics of diodes and

transistors. Solve basic problems in electronic circuits. Implement different applications using basic electronic

devices (diodes and transistors). Read and understand the datasheets of diodes and transistors

to use the suitable parts in design. Design and analyze electronic circuits use computer

packages (simulators). Acquire better skills in performing the laboratory experiments. Work as a team in laboratory sessions.

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Electronic Circuit Design Steps

• Theory: Semiconductor Physics, Circuit Theory.

• Analysis: DC and AC (small and large signal)modeling

• Simulation: CAD Tools, Spice and derivatives• Implementation: Breadboard and PCB

Testing.

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Simulators

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Multisim (National Instruments)

TINA

LTSPICE

Altium, Proteus, Cadence (Advanced and

licensed)

https://www.eetimes.com/document.asp?doc_id=13

26778#

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• 1.1 Electronics versus Microelectronics

• 1.2 Example of Electronic System: Cellular Telephone

• 1.3 Analog versus Digital

Chapter 1 Why Microelectronics?

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Why Electronics?

CH1 Why Microelectronics? 12

Cellular Technology

• An important example of microelectronics.• Microelectronics exist in black boxes that process the

received and transmitted voice signals.

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Frequency Up-conversion

• Voice is “up-converted” by multiplying two sinusoids.• When multiplying two sinusoids in time domain, their

spectra are convolved in frequency domain.


Transmitter

• Two frequencies are multiplied and radiated by an antenna in (a).

• A power amplifier is added in (b) to boost the signal.

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Receiver

• High frequency is translated to DC by multiplying by fC.• A low-noise amplifier is needed for signal boosting without

excessive noise.


Digital or Analog?

• X1(t) is operating at 100Mb/s and X2(t) is operating at 1Gb/s.

• A digital signal operating at very high frequency is very “analog”.

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Chapter 2 Basic Physics of Semiconductors

• 2.1 Semiconductor materials and their properties

• 2.2 PN-junction diodes

• 2.3 Reverse Breakdown

CH2 Basic Physics of Semiconductors 18

Semiconductor Physics

• Semiconductor devices serve as heart of microelectronics.

• PN junction is the most fundamental semiconductor device.

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Charge Carriers in Semiconductor

• To understand PN junction’s IV characteristics, it is important to understand charge carriers’ behavior in solids, how to modify carrier densities, and different mechanisms of charge flow.


Periodic Table

• This abridged table contains elements with three to five valence electrons, with Si being the most important.

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Valence Electrons• Valence electrons: electrons in the outermost shell.

– Electrons that are in orbits farther from the nucleus have higher energy and are less tightly bound to the atom than those close to the nucleus.

– Electrons with the highest energy exist in the outermost shell of an atom and are relatively loosely bound to the atom.

Silicon Atom

Silicon has four valence electrons.

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Sharing of Electrons in Silicon

A silicon atom with its four valence electrons shares an electron with each of its four neighbors. This effectively creates eight shares valence electrons for each atom and produces a state of chemical stability.The sharing of valence electrons produce the covalent bonds that hold the atoms together; each valence electron is attracted equally by the two adjacent atoms which share it.


Silicon

• Si has four valence electrons. Therefore, it can form covalent bonds with four of its neighbors.

• When temperature goes up, electrons in the covalent bond can become free.

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Sharing of Electrons in Silicon

At T=0K

Electrons gain thermal energy and break away from the bonds. They begin to act as “free charge carriers”—free electron.

An electron leave behind a void because the bond is now incomplete. A void is called a hole. A hole can absorb an free electron if one becomes available.

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One electron has traveled from right to left.One hole has traveled from left to right.

Bandgap EnergyQ:Does any thermal energy create free electrons (and holes) in silicon?

A: No. A minimum energy—called the “bandgap energy” is required to dislodge an electron from a covalent bond. For silicon, the bandgap energy is 1.12 eV. Note: eV represents the energy necessary to move one electron across a potential difference of 1V. 1 eV =1.6 x 10-19 J

Insulators display a higher Eg . (e.g. 2.5 eV for diamond)Semiconductors usually have a moderate Eg between 1 eV and 1.5 eV.

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Electron DensityQ: How many free electrons are created at a given temperature?

15 3 2 35 2 10 exp electrons cm2

gi

En T

kT

where k=1.38 x 10-23 J/K is called the Boltzmann constant.

As expected, materials having a larger bandgap(Eg)exhibit a smaller ni . Also, as T approaches zero, niapproaches zero.

Making sense of electron density

Determine the electron density in silicon at T=300K.Use the electron density formula with Eg=1.12 eV, ni @ 300 T is 1.08 x 1010

Electrons per cm3.

Silicon has 5 x 1022 atoms per cm3.

What this means is that there is one electron for 5 x 1012 atoms at room temperature.

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Intrinsic Semiconductor

The pure silicon has few electrons incomparison to the numbers of atoms.Therefore, it is somewhat resistive.

In an intrinsic semiconductors, the electrondensity(n or ni) is equal to the hole density (p).(each electron is created by leaving behind ahole.)So

np=ni2

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Free Electron Density at a Given Temperature

• Eg, or bandgap energy determines how much effort is needed to break off an electron from its covalent bond.

• There exists an exponential relationship between the free-electron density and bandgap energy.

3150

3100

32/315

/1054.1)600(

/1008.1)300(

/2

exp102.5

cmelectronsKTn

cmelectronsKTn

cmelectronskT

ETn

i

i

gi


Doping (N type)

• Pure Si can be doped with other elements to change its electrical properties.

• For example, if Si is doped with P (phosphorous), then it has more electrons, or becomes type N (electron).

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Phosphorus has 5 valence electrons. The 5th electron is “unattached”. This electron is free to move and serves as a charge carrier.

Doping

The controlled addition of an impurity such as phosphorus to an intrinsic (pure) semiconductor is called “doping”. And phosphorus itself is a dopant.

Providing many more free electrons than in the intrinsic state, the doped silicon crystal is now called “extrinsic,” more specifically, an “ n-type” semiconductor to emphasize the abundance of free electrons.

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Hole density in an n-type semiconductor

Many of the new electrons donated by the dopant “recombine” with the holes that were created in the intrinsic material. As a consequence, in an n-type semiconductor. The hole density will drop below its intrinsic level.

np=ni2

In an n-type semiconductor, Electrons are the majority carriers.Holes are the minority carriers.If a voltage is applied across an n-type materials, the current consists predominantly of electrons.


Doping (P type)

• If Si is doped with B (boron), then it has more holes, or becomes type P.

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if we can dope silicon with an atom that provides an insufficient number of electrons, then we may obtain many incomplete covalent bonds.A boron has only 3 valence electrons and can form only 3 covalent bonds. Therefore, it contains a hole and is ready to absorb a free electron.

Summary

MajorityCarriers Dn N 2

MinorityCarriers i

D

np

N

MajorityCarriers Ap N 2

MinorityCarriers i

A

nn

N

In n-type material,

In p-type material,

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Summary of Charge Carriers


First Charge Transportation Mechanism: Drift

• The process in which charge particles move because of an electric field is called drift.

• Charge particles will move at a velocity that is proportional to the electric field.

Ev

Ev

ne

ph

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Current Flow: General Case

• Electric current is calculated as the amount of charge in v meters that passes thru a cross-section if the charge travel with a velocity of v m/s.

qnhWvI


Epnq

qpEqnEJ

qnEJ

pn

pntot

nn

)(

Current Flow: Drift

• Since velocity is equal to E, drift characteristic is obtained by substituting V with E in the general current equation.

• The total current density consists of both electrons and holes.

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Velocity Saturation

• A topic treated in more advanced courses is velocity saturation.

• In reality, velocity does not increase linearly with electric field. It will eventually saturate to a critical value.

E

v

Ev

bv

bE

sat

sat

0

0

0

0

1

1


Second Charge Transportation Mechanism: Diffusion

• Charge particles move from a region of high concentration to a region of low concentration. It is analogous to an every day example of an ink droplet in water.

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Current Flow: Diffusion

• Diffusion current is proportional to the gradient of charge (dn/dx) along the direction of current flow.

• Its total current density consists of both electrons and holes.

dxdn

qDJ

dxdn

AqDI

nn

n

)(dxdp

Ddxdn

DqJ

dxdp

qDJ

pntot

pp


Example: Linear vs. Nonlinear Charge Density Profile

• Linear charge density profile means constant diffusion current, whereas nonlinear charge density profile means varying diffusion current.

LN

qDdxdn

qDJ nnn dd

nn L

xL

NqDdxdn

qDJ

exp

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Einstein's Relation

• While the underlying physics behind drift and diffusion currents are totally different, Einstein’s relation provides a mysterious link between the two.

qkTD

Documents

ese206 SP 2019 lecture 1 intro · Develop an understanding of the Bipolar Junction Transistor (BJT) and its operation. Identify and describe the different BJT configurations, DC biasing,